Altitude corrected landing system for aircraft



Dec. 5, R50 .J. D. PETERSON ALTITUDE CORRECTED LANDING SYSTEM FOR AIRCRAFT' Filed April 18, 1947 INVENTOR. JUEL D. PETEHEUN Patented Dec. 5, 1950 ALTITUDE ooim'iicriin LANDING SYSTEM roanmoaarr .l'oei 'iDfiPeter son,"Ridgewood, N. J; assignor to Bendix Aviation Corporation, Teterboro, N. 3.,

a corporation of; Delaware 1 App1ication ap $1 1.18, 1947, Serial No. 742,439

Hi -his 5 A invention relates to" 'a'it'ZiIn'atic 7 landing systems for 'aircraft, andmore particularly'toflan altitude corrected landingsystm for controlling the airspeed cf aircraft on landing approaches and for synchronizing" the speeds of the engines on ni'ulti' engiiied"aircraft-L This application is an improvement onfth'e' Engine CohtroVahd Synchronization System shown in my co-pending application bearing Serial No. 742,438 and filed on April 1 8; 1947': automatic landing systems two'radio beams, signalmodulatedyare broadcast fromthe airfield for-'*=lancl-ing aircraft svlitably equipped with the necessary i adio receiver -computer; and flight surface controls. one bea'in of the landingsy's tem-gene'rally know'rr'asthe localizerbeamf ill" by' its signal' voltages bring in aircraft=ovr"a' particular flight" strip. 'The other -beae1;-known as the glide path control 'bea'fn, will 'bring"'d0wn 12 Claims. (Cl. 244-77) k 2 a "strip at'Me'xi'co City mayprove disastrous in view of] the, diiierencef'in air density at these elevations. To maintain controlled flight in descending from approximately 1,000 feet above Mexico city the throttle posi tion;must be shifted to'provide a greater air intake tha n in descending at the airport "atWashingtom D. C.

It is, therefore, an obiec't "of my present invene tion to provide 'an 'altitudecorrectedfcontrol circuitfor-controlling the engineitorque of aircraft in response' to" sig'nah' voltagesdeveloped by a computer in" the glide path c'ontrol beam channel of an automatic landing system.

aircraft --onto thepartic'ular flight strip. Such-a system is fully described in the copending -'a 1: p1i'-'- cation of Paul Noxon et-al'. for "Automatic Control. of-= Mobile' 'Craftbearing-Serial No. 705 524,. and-'fi-led'on-October ;"1946:

- In my -parent application; I have described "an 25 engine control systemwherein the speed" of" the" aircraftengine' iscontrolled bythe signals ofthe glide 'path beam and in which, in the 'case' of multi-engined craft; the engine speeds "are synchronized As is well-known in'the art, aircraft" engine speed='---isreduced when approaches 'are" madefor landing. The system 'describedinthe' parent case will reduce the speed of'engine-opera tion in-responseto the computer sigma-1* voltages, the engines being maintained in synchronism at all times;

The system asdeScr-ibedinmy parent applica= tion will operate satisfactorily when 'va'ircraft thus equipped -arefiying routes wherein the various ports of -call -are---approximately at the" 40 same altitude; as for -'example',-those airlines servicing the eastern coast ot-North and South" America. Inthe caseoftranscontinental routes it was found that-an altitude --correction was" necessaryto permit landings-at airfields'at varying altitudes such as the airports at New York cityor Washington,;D. (1., approximately at sea level, and at Denver, Colorado, "or Mexico City,

where the altitude iswell over 5,0O0'feet1 .As' previously stated, the glidepath beam is used .to" bring down aircraft on a particular flight strip by actuation of the elevators and-by {reducing the torque of the engines. The same reduction airspeed, however,- at-LOOO feet above an air strip located at Washington, D. 0., and over voltages; while engined plane.

which shall beentirely automatic in its opera tion, positive in its action, and relatively inexpensive to manufacture, which shall have a large variety ofapplications, 'andyet be practical and efiicient'to'a high degree in'use. Other objects ofthis invention will in part be obvious; and in" part' hereinafter pointed out.

'The invention accordingly consists in features of construction, combinations 'of'elements, and

arrangementso'f parts whichwill be exemplified in the constructionhereinafter described, and of which'the pe p'plication will be indicated in the appended'claims: 7 Y r In the accompanying drawings forming a part of this specification in which'two of'the various possible illustrative embodiments of inven tion are shown, and" wherein similar reference characters designate corresponding elements in thetwo'views,

1 is a schematic wiring diagram of'an" altitude corrected control circuit for controlling the engine torque of aircraft in response to signal Fig. 2'is a schematic wiring diagram of an alti tude corrected control system for controlling the torque and's'ynchronizing the engines of a multi- Referring now to Fig. l 'of the drawings, iii designates a control'circuit embodying my inven"-' tion for controllingthe torque of an engine it having "a throttle control lever i2 for altering the speed of engine operation. Thecircuit it! interconnects a" source "of signal voltage is forming the output terminals of a computer (not shown) in the glide path control channel of a receiver, with a two phase induction motor M for moving the throttle lever I2.

The induction motor 14 comprises a fixed phase connected across a suitable source of potential it, a variable phase i'l fixed to the output of an amplifier i8, and a rotor !9. The rotor I5 is geared or coupled in a suitable manner as indicated by the dotted line 26, to shift the throttle lever !2 upon rotation thereof.

The induction motor is further coupled as by 2!, to a synchronous motor, receiver, or rotary transformer 22. The receiver 22 comprises a retor 23 coupled to rotor !9 and connected to the source of potential l5, and a stator windin 2% connected at one end by lead 25 to one terminal of the signal source I3. The other end of the winding is connected by lead 25 to an input terminal of the amplifier [8. The other amplifier terminal is connected by lead 2? to the second terminal of the signal source.

The signal voltage of the source !3 is balanced by the voltage induced in stator winding 2 by the positioning of the receiver rotor 23. No voltage is supplied to the input side of the amplifier H3. The induction motor is thus at a standstill. Upon a change in the signal voltage, the circuit described is unbalanced to operate the induction motor M. The rotation of the rotor 19 will posi-- tion the receiver rotor 23 to rebalance the circuit, at the same time shifting the throttle lever !2 to a new position in response to the signal voltage, to decrease (or increase) the torque delivered.

Means is now provided to introduce into the control circuit described a signal voltage which is proportional to the altitude of the plane in which the present system is installed.

To this end, there is provided an aneroid capsule 3B, the exterior of which is subjected to atmospheric pressure. Integral with said aneroid is a stud 3! having pivoted at its free end an arm 32. The other end of arm 32 is keyed to a shaft 33 to which is fixed a sector gear 34. The teeth of the sector gear mesh with the teeth of a pinion 35 carried by a shaft 35. Coupled to the shaft in a suitable manner is a synchronous generator, transmitter, or rotary transformer 13?.

The transmitter 3'! comprises a stator win ing 38 connected into the lead 2'! of the signal source !3, and a rotor winding 39 angularly displaceable by shaft 35 and connected across the power suppl IS. The expansion and contraction of the aneroid 35 will displace the transmitter rotor 39. The voltage induced in the stator winding 38 b the rotor 39 will vary in accordance with the changes in the altitude of the aircraft.

The induced voltage in stator winding 38 is in series with the signal voltages of the source !3. Thus, a signal voltage representative of the altitude of the aircraft is added into the control circuit to be balanced by the receiver 22. A change in either the signal voltage of source !3, or in the signal voltage of the altitude transmitter 3'! will unbalance the control circuit requiring an angular displacement of the receiver rotor 23. The throttle lever 12 will be shifted accordingly in rebalancing the circuit to provide an engine speed in conformity with the beamed signals and the altitude of the plane.

Referring now to Fig. 2 of the drawings, I have illustrated an altitude corrected system for a multi-engined plane, the engine l and its altitude corrected system being incorporated therein as the master engine together with an engine designated 5! and hereinafter referred to as the slave engine.

The slave engine El is provided with a throttle control lever 12 for controlling the speed thereof. An induction motor 44 is provided having a fixed phase 55, a variable phase 5'! connected to the output of an amplifier 48, and a rotor 49 coupled as by 55, to the lever $2. The rotor 59 is also adapted to drive a receiver 52 through a coupling 51.

The receiver 52 has a rotor coil 53 connected across power supply [5 and a stator winding 55 connected by lead 55 to the lead 25 of the signal source !3. The other side of the stator winding is connected by wire 55 to an input terminal of the amplifier 48 and by wire 5! to the input lead 2'6 of the amplifier !8.

The two control circuits for the engines I! and 4! are thus connected in parallel across the signal source !3 and the altitude signal source (stator 38). Unbalance of the circuits by changes in beamed signal voltage or in altitude signal voltage will operate the motors l4 and M in the manner hereinbefore described, to rebalance the circuits and control the engine speeds in accordance with the beamed signals and the altitude of the plane.

Means is now provided to bring the speed of engine 4! into absolute synchronism with that of engine H.

To this end, engines I! and M are provided with synchronous generators or transmitters having rotors 5! connected across the power supply H5 and coupled to the propellor shaft as indicated by the dotted line 52; and a three phase stator winding 53. A differential motor 54 is also provided having three phase stator and rotor windings 55 and 56. The stator winding 55 is connected by leads 5'! to the slave stator winding, while the rotor winding 56 is connected by leads 58 to the master stator winding.

The rotation of the generator rotors 5! by their respective propellor shafts will induce a voltage in the stator windings resulting in a rotating magnetic field in the stator, the speed of which is a function of the engine speed. A difference in the speeds of the engines I! and 4! will cause a difference in the speeds of the rotating magnetic fields of the stator and rotor windings of the differential motor 5 The reaction of the magnetic fields will cause the rotor winding 56 to rotate at a speed proportional to the difference in engine speeds.

A synchronous generator, transmitter, or rotary transformer 6!! is provided to produce a signal voltage proportional to the difference in engine speed, which is impressed on the slave motor circuit to bring the same into synchronism.

The transmitter 60 comprises a rotor coil 6! connected across the power supply H5 and coupled to the differential rotor 56 as by 52, and a stator winding 63. The winding 63 is connected into the lead 5! in series with the signal voltage source I3 and the altitude voltage source (stator) 38.

Any difference in the speed of engines H and d2 will cause the rotor 6! to be displaced for inducing a signal voltage in the winding 53. This signal voltage will unbalance the slave engine control circuit to bring about the operation of motor 44 to rebalance the circuit and change the speed of engine 4! to correspond with that of engine H, as fully described in my parent application.

It will be readily appreciated by those skilled in the art, that the inductive devices 22, 31, 52, and 60 may readily be replaced by other sources of variable potential, or by devices for varying the strength of the signal voltages of source 13.

It will be thus seen that there is provided an altitude corrected control and synchronization system in which the several objects of this invention are achieved and which is welladapted to meet the conditions of practical use.

As various possible embodiments of the invention may be made, and as various changes may be made in the embodiment above set forth, it is to be understood that all matter herein set forth, or shown in the accompanying drawing, is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim as new and desire to secure by Letters Patent:

1. In an automatic landing system for aircraft,

the combination of a source of signal voltage controlled by the glide path beam channel of the system with means for regulating the airspeed of a craft, a circuit interconnecting said signal source with said regulating means including two windings therein, means for inducing in one of said windings a voltage proportional to the altirude of the craft, and means for inducing a voltage in the other of said windings to offset the voltages of said source and the other of said windings, the unbalance of said circuit operating said regulating means, the operation of said regulating means controlling the balancing voltages induced in said second winding to rebalance said circuit.

2. In an automatic landing system for aircraft in which a radiant energy beam is received aboard the craft and the signal voltages derived therefrom are utilized to control landing of the craft, the combination of the source of said signal voltages with means for regulating the aircraft engine torque in response to said signal vol ages, and means for varying the signal voltages in accordance with the altitude of the aircraft.

3. In an automatic landing system for aircraft in which a radiant energy beam is received aboard the craft and the signal volta es derived therefrom are utilized to control landing of the craft, the combination of the source of said signal voltages with means for regulating the aircraft engine torque, motive means responsive to said signal voltages for actuating said regulating means, and means for varying the operation of said motive means in accordance with the altitude of the craft.

4. In an'automatic landing system for aircraft in which a radiant energy beam is received aboard the craft and the signal voltages derived therefrom are utilized to control landing of the craft, the combination of the source of said signal voltages with means for regulating the torque of an aircraft engine, motive means for actuating said regulating means, and a source of signal voltage proportional to the altitude of the aircraft, said first and second voltage sources controlling the operation of said motive means.

5. In an automatic landing system for aircraft in which a radiant energy beam is received aboard the craft and the signal voltages derived therefrom are utilized to control landing of the craft, the combination of the source of said signal voltages with means for regulating the torque of an aircraft engine, motive means for actuating said regulating means, and a source of signal voltage proportional to the altitude of the air- 6 craft, said first and second signal sources being in and controlling the operation of said motive means.

6. In an automatic landing system for aircraft which :a radiant energy beam is received aboard the craft and the signal voltages derived therefrom are utilized to control landing of the craft, the combination of the source of said signal voltages with means for regulating the torque of an aircraft engine, motive means controlling said regulating means, a balanced circuit interconnecting said source and said motive means, and means for impressing on said circuit 9. voltage proportional to the altitude of the aircraft, said circuit being unbalanced by changes in the signal voltages of said source and by the impression of the altitude voltages to operate said motive means. In an automatic landing system for aircraft in a radiant energy beam is received aboard the craft and the signal voltages derived therefrom are utilized to control landing of the craft, the combination of the source of said sigrial voltages with means for regulating the torque of an aircraft engine, motive means controlling said regulating means, a balanced circuit interconnecting said source a-nd said motive means, means for impressing on said circuit a voltage proportional to the altitude of the aircraft, said circuit being unbalanced by changes in the signal voltages of said source and by the impression of the altitude voltages to operate said moti e means, and means controlled by said motive means for rebalancing said circuit upon opera-- tion of said motive means.

8. In an automatic landing system for aircraft in which a radiant energy beam is received aboard the craft and the signal voltages derived therefrom are utilized to control landing of the craft, the combination of the source of said signal voltages with means for regulating the airspeed of aircraft with motive means for controlling said regulating means, a circuit interconnecting said voltage source and said motive means including a source of potential variable with altitude, and a source of balancing potential to offset the voltages of said first and second sources to balance said circuit, an unbalance of said circuit operating said motive means to regulate the airspeed of the craft.

9. In an automatic landing system for aircraft in which a radiant energy beam is received aboard the craft and the signal voltages derived therefrom are utilized to control landing of the craft, the combination of the source of said signal voltages with means for regulating the airspeed of aircraft and motive means for controlling said regulating means, a circuit interconnecting said voltage source and said motive means including a source of potential variable with altitude, and a source of balancing potential to offset the voltages of said first and second sources, an unbalance of said circuit operating said motive means to regulate the airspeed of the craft, and means controlled by said motive means for varying the balancing potential to rebalance said circuit upon operation thereof when the airspeed of the craft is in agreement with the voltage signals and the altitude potential.

10. In an automatic landing system for aircraft in which a radiant energy beam is received aboard the craft and the signal voltages derived therefrom are utilized to control landing of the craft, the combination of the source of said signal voltages with a throttle control for an aircraft engine, a motor adapted to position said control, a circuit interconnecting said motor and source, an induction device in said circuit adapted to impress a voltage on said circuit in response to the altitude of the aircraft, and a second induction device in said circuit adapted to impress a voltage on said circuit to balance the voltages of said source and said first device, a change in signal voltage or in the altitude voltage unbalancing said circuit to operate said motor.

11. In an automatic landing system for aircraft in which a radiant energy beam is received aboard the craft and the signal voltages derived therefrom are utilized to control landing of the craft, the combination of the source of said signal voltages with a throttle control for an aircraft engine, a motor adapted to position said control upon operation thereof, a circuit interconnecting said motor and source, an induction device in said circuit adapted to impress a voltage on said circuit in response to the altitude of the aircraft, and a second induction device in said circuit to balance the voltages of said source and said first device, a change in signal voltage or in the altitude voltage unbalancing said circuit to operate said motor, the voltage of said second induction device being varied by the operation of said motor to ofiset the signal and altitude voltages when throttle control position is in agreement with said voltages.

12. In a system for controlling the landing of multi-engined aircraft automatically in which a radiant energy beam is received aboard the craft and the signal voltages derived therefrom are utilized to control landing of the craft, the combination of the source of said signal voltages with a second source of signal voltage variable with the altitude of the aircraft and connected to said first source, a circuit for controlling the engine torque of each engine and connected across said first and second sources, and means responsive to the difierence in engine speeds to synchronize the operations of the engines.

JOEL D. PETERSON.

REFERENCES CITED Ihe following references are of record in the file of this patent:

UNITED STATES PA IniNTS Number Name Date 1,997,412 Fischel Apr. 9, 1935 2,133,285 Dunmore Oct. 18, 1938 2,143,137 Basim et a1. Jan. 10, 1939 2,323,311 Crane et a1. July 6, 1943 2,423,336 Moseley July 1, 1947 

